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Physiology Fall 21' > CH. 14 Cardiovascular System: Blood Vessels, Blood Flow, and Blood Pressure > Flashcards

CH. 14 Cardiovascular System: Blood Vessels, Blood Flow, and Blood Pressure Flashcards

1
Q

What two physical laws govern blood flow and blood pressure?

A

pressure gradients and resistance in the cardiovascular system

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2
Q

How is the circulatory system a closed system?

A

there is no input or output but is rather just constant

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3
Q

What is the equation for flow?

A

change in pressure/resistance

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4
Q

What drives flow from high pressure to low pressure in the cardiovascular system?

A

pressure gradients (bulk flow)

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5
Q

What is the change in pressure across the systemic circuit?

A

pressure in aorta (MVP) minus pressure in vena cava (CVP) just before it empties into right atrium

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6
Q

What is change in pressure across the pulmonary circuit?

A

pressure in pulmonary arteries minus pressure in pulmonary veins

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7
Q

T/F does blood in pulmonary circuit service the lungs

A

False; pulmonary circuit is meant only for gas exchange

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8
Q

Is the pressure gradient greater in the systemic circuit or pulmonary circuit?

A

systemic circuit; resistance in pulmonary circuit is much less than resistance through the systemic circuit

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9
Q

What three factors affect resistance to flow?

A
  1. radius of vessel
  2. length of vessel
  3. viscosity of fluid
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10
Q

What is blood viscosity dependent on?

A

amount of RBCs and proteins - usually constant

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11
Q

How does arteriole radius affect blood flow?

A

Vasoconstriction: decreased radius -> increased resistance

Vasodilation: increased radius -> decreased resistance

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12
Q

What is total peripheral resistance?

A

combined resistance of all blood vessels within the systemic circuit

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13
Q

What does vasoconstriction in network of blood vessels lead to?

A

increased resistance -> decreased flow

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14
Q

What does vasodilation in network lead to?

A

decreased resistance -> increased flow

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15
Q

How would you relate pressure gradients and resistance in the systemic circulation?

A

Flow = Cardiac output

Change in pressure = mean arterial pressure

Resistance = total peripheral resistance

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16
Q

How do arteries act as a pressure reservoir?

A

they have thick, elastic arterial walls that push blood through system
- expand during systole and recoil during diastole

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17
Q

What structural features make arteries a rapid transport pathway?

A

large diameter and little resistance

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18
Q

What is compliance? What is meant by low compliance and high compliance?

A

measure of how the pressure of a vessel will change with a change in volume

  • Low compliance: small increase in blood volume causes a large increase in pressure
  • High compliance: large increase in blood volume is required to produce a large increase in pressure
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19
Q

What is observed when measuring the blood pressure of a compressed artery?

A

turbulent flow produces Korotkoff sound

- pressure at first Korotkoff sound = systolic blood pressure

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20
Q

What is observed when measuring the blood pressure of an uncompressed artery?

A

laminar flow, no sound

- pressure when sound disappears = diastolic blood pressure

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21
Q

What is the equation for mean arterial pressure (MAP)?

A

MAP = [SP + (2 x DP)]/3

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22
Q

What are resistant vessels?

A

arterioles; connect arteries to capillaries or metarterioles

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23
Q

What factors affect arteriole radius?

A
  1. contraction state of smooth muscle in arteriole wall
  2. arteriolar tone: contraction level is independent of extrinsic influences
  3. vasoconstriction: increased contraction = decreased radius
  4. vasodilation: decreased contraction = increased radius
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24
Q

What are the two functions of varying arteriole radius?

A
  1. controlling blood flow to individual capillary beds

2. regulating mean arterial pressure

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25
Q

What is regulation of blood flow to organs based on?

A

need

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26
Q

What local factors control vascular resistance?

A
  1. changes in radius of arterioles
  2. depends on contractile state of smooth muscle in walls of the vessel
  3. local factors regulate, thereby regulate blood flow
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27
Q

What do changes associated with increased metabolic activity generally cause?

A

vasodilation

  • carbon dioxide
  • potassium
  • hydrogen ions
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28
Q

What do changes associated with decreased metabolic activity generally cause?

A

vasoconstriction

- oxygen

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29
Q

What is active hyperemia?

A

increased blood flow in response to increased metabolic activity

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30
Q

What occurs as a result of active hyperemia in organs?

A
  1. increased metabolic rate
  2. response to low oxygen and high carbon dioxide
  3. increased blood flow
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31
Q

What is reactive hyperemia?

A

increased blood flow in response to a previous reduction in blood flow

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32
Q

What occurs when there is a blockage of blood flow to tissues?

A

metabolites increase and oxygen decreases but once blockage is released, metabolites are removed and oxygen is delivered as blood flow increases due to low resistance

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33
Q

What is a myogenic response?

A

change in vascular resistance in response to stretch of blood vessels in the absence of external factors

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34
Q

What is the purpose of myogenic auto-regulation of blood flow?

A

to keep blood flow constant

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35
Q

What are the big 4 local vasoactive substance and what are their effects on vascular smooth muscle?

A
  1. oxygen: vasoconstriction
  2. carbon dioxide: vasodilation
  3. potassium ions: vasodilation (vasoconstriction at high concentrations)
  4. acids (hydrogen ions): vasodilation
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36
Q

How is blood distributed during exercise?

A
  • Dilation of vessels to skeletal muscle and heart increases blood flow to muscles
  • Constriction of vessels to GI tract and kidneys decreases blood flow to these organs
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37
Q

What is mean arterial pressure dependent on?

A

total peripheral resistance

38
Q

What is total peripheral resistance dependent on?

A

radius of arterioles

39
Q

What extrinsic mechanisms regulate the radius of arterioles to control MAP?

A
  1. sympathetic activity

2. hormones

40
Q

How doe TPR and MAP increase when arteriolar radius is under sympathetic control?

A

norepinephrine binds to alpha adrenergic receptors and vasoconstriction is produced

41
Q

What adrenergic receptors are present in arterioles to skeletal and cardiac muscle?

A

both alpha and beta 2 receptors

42
Q

What binds to alpha adrenergic receptors and what occurs?

A

norepinephrine binds to alpha receptors and vasoconstriction occurs

43
Q

What binds to both alpha and beta 2 receptors and what occurs?

A

epinephrine binds to both

  • vasoconstriction at alpha receptors
  • vasodilation at beta 2 receptors
44
Q

What adrenergic receptor does epinephrine have a greater affinity for?

A

beta 2 receptors

45
Q

What effect do sympathetic nerves have on arteriole radius?

A

vasoconstriction

46
Q

What effect does epinephrine have on arteriole radius?

A

alpha adrenergic: vasoconstriction

beta 2 adrenergic: vasodilation

47
Q

What effect does vasopressin have on arteriole radius?

A

vasoconstriction

48
Q

What effect does angiotensin II have on arteriole radius?

A

vasoconstriction

49
Q

Which blood vessel has the slowest velocity of blood flow?

A

capillaries; slow blood flow enhances exchange between blood and tissue

50
Q

What is allowed to move through continuous capillaries?

A

small water soluble molecules

51
Q

What is allowed to move through fenestrated capillaries?

A

proteins, and in some cases blood cells

52
Q

What are metarterioles and what do they function as?

A

they are intermediate between arterioles and capillaries that directly connect arterioles to venules
- function as shunts to bypass capillaries

53
Q

What does contraction and relaxation of the smooth muscle of metarterioles do?

A

contraction: decrease blood flow through capillaries
relax: increase blood flow through capillaries

54
Q

What are pre-capillary sphincters?

A

rings of smooth muscle that surround capillaries on the arteriole end
- only contract and relax in response to local factors

55
Q

What does contraction and relaxation of pre-capillary sphincters do?

A

contraction: constricts capillary which decreases blood flow
relaxation: increases blood flow

56
Q

What is the most common mechanism to exchange across capillary walls?

A

diffusion

  • lipophilic: across membrane
  • lipophobic: through channels
57
Q

What are the 3 ways that exchange can occur across capillary walls?

A
  1. diffusion
  2. transcytosis: exchangeable proteins
  3. mediated transport: in brain
58
Q

What kind of movement is filtration across capillaries?

A

Movement out of capillary into interstitial space

59
Q

What kind of movement is absorption across capillaries?

A

Movement into capillary from interstitial space

60
Q

What are the 4 starling forces across the capillary walls?

A
  1. Capillary hydrostatic pressure
  2. Interstitial fluid hydrostatic pressure
  3. Capillary osmotic pressure
  4. Interstitial fluid osmotic pressure
61
Q

What is the equation for net filtration pressure?

A

NFP = filtration pressure - absorption pressure

62
Q

What is the role of the lymphatic system during blood circulation?

A

picks up excess filtrate and cleans and returns it to circulation

63
Q

What are some factors that affect filtration and absorption across capillaries?

A
  1. standing on feet - increases hydrostatic pressure
  2. injuries
    - when capillaries are damaged, they leak fluid and proteins
    - histamine increases capillary permeability to proteins
  3. liver disease
    - decreases plasma proteins
    - not enough plasma proteins lowers level of reabsorption
  4. kidney disease
  5. heart disease
64
Q

What are venules?

A

connect capillaries to veins with little smooth muscle in walls

65
Q

What allows unidirectional blood flow in veins and where are they present?

A

valves

  • present in peripheral veins
  • absent from central veins
66
Q

What makes veins compliant vessels?

A
  1. expand with little change in pressure
  2. function as blood reservoir
  3. 60% of the total blood volume in systemic veins are at rest
67
Q

What 4 factors influence venous pressure and venous return?

A
  1. skeletal muscle pump: one way valves in peripheral veins
    - blood moves toward heart when contracted
    - blood flows into veins between muscles when relaxed
  2. respiratory pump:
    - inspiration decreases pressure in thoracic and increases pressure in abdominal
    - pressure in abdominal creates favorable gradient for movement to thoracic
  3. blood volume
    - increased blood volume -> increased venous pressure
    - decreased blood volume -> decreased venous pressure
  4. venomotor tone: smooth muscle tension in the veins
    - increases central venous pressure
    - decreases venous compliance
    - increases venous return
68
Q

What is the smooth muscle in the walls of veins innervated by?

A

sympathetic nervous system

69
Q

What hormone acting at the alpha adrenergic receptors causes venous constriction?

A

norepinephrine

70
Q

Where do lymphatic veins drain lymph fluid?

A

into the thoracic duct which empties into the right atrium

71
Q

What are the three determinants of mean arterial pressure (MAP)?

A
  1. heart rate
  2. stroke volume
  3. total peripheral resistance
72
Q

What causes hypotension?

A

mean arterial pressure is less than normal and is caused by inadequate blood flow to tissues

73
Q

What causes hypertension?

A

mean arterial pressure is greater than normal and is a stressor for heart and blood vessels when prolonged

74
Q

How is mean arterial pressure regulated in the short term?

A

primarily neural control that regulates cardiac output and total peripheral resistance
- involves the heart and blood vessels

75
Q

How is mean arterial pressure regulated in the long term?

A

primarily hormonal control that regulates blood volume and involves the kidneys

76
Q

Lay out the negative feedback loop used in neural regulation of mean arterial pressure.

A

Detector = baroreceptors
Integration center = cardiovascular centers in the brainstem
Controllers = autonomic nervous system
Effectors = heart and blood vessels

77
Q

What are baroreceptors?

A

pressure receptors that respond to stretching due to pressure changes in arteries

78
Q

What are the two arterial baroreceptors?

A

aortic arch and carotid sinuses

79
Q

What is the cardiovascular control center comprised of?

A

medulla oblongata which is the integration center for blood pressure regulation

80
Q

What is the input (5) and output (2) of the cardiovascular control center?

A

Input:

  • arterial baroreceptors
  • low pressure baroreceptors
  • chemoreceptors (oxygen and carbon dioxide)
  • proprioceptors
  • higher brain centers

Output:

  • sympathetic nervous system
  • parasympathetic nervous system
81
Q

What occurs during autonomic output to cardiovascular effectors?

A

Parasympathetic input to SA node (decreases HR) -> AV node

Sympathetic input to SA node (increases HR) -> AV node -> ventricular myocardium (increases contractility) -> Arterioles (increases resistance) -> Veins (increases venomotor tone)

82
Q

What is the framework of maintaining blood pressure at normal level?

A

baroreceptor reflex

  • Detectors - baroreceptors
  • Afferents - visceral afferents
  • Integration center - cardiovascular control center
  • Efferents - autonomic nervous system
  • Effectors - heart, arterioles, and veins
83
Q

What 3 hormones provide long term mean arterial pressure regulation?

A
  1. epinephrine
  2. vasopressin
  3. angiotensin II
84
Q

How does epinephrine increase mean arterial pressure?

A
  1. acts on smooth muscle of arterioles (increases TPR)
  2. acts on smooth muscle of veins (increases venomotor tone)
  3. acts on heart (increases HR and SV)
85
Q

How do vasopressin and angiotensin II regulate mean arterial pressure?

A

vasoconstrictors that increase TPR and MAP

86
Q

What do low-pressure baroreceptors do and where are they found?

A

decrease in blood volume activates receptors which trigger responses that act in parallel with the baroreceptor reflex
- found in walls of large systemic veins and walls of atria

87
Q

How does respiratory sinus arrhythmia regulate heart rate?

A

during inspiration:
- sympathetic activity increases -> heart rate increases

during expiration:
- parasympathetic activity increases -> heart rate decreases

88
Q

What effect do chemoreceptors have on ventilation when carbon dioxide levels are increased in the blood?

A

carbon dioxide increases which in turn increases TPR and decreases HR
- MAP generally increases

89
Q

How is thermoregulation mediated and how does it regulate cardiovascular responses?

A

through hypothalamus

  • an increase in body temperature leads to: decrease sympathetic activity to skin
  • vasodilation to skin
  • increase heat loss to environment
90
Q

What is more important to cardiovascular regulatory responses: baroreceptor reflex or thermoregulation?

A

thermoregulation

Physiology Fall 21' (15 decks)

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